I am right in the middle of working on a Sudoku quilt right now. No numbers, just the colors work into a valid puzzle. I used blank address stickers on each square with the number on it to make certain that I didn't mix up the squares. I also added a panel at the top to add extra length and put 4 stars on that panel close to the puzzle to show the difficulty of the puzzle (as most puzzles are rated that way).
When it's done, I promise I'll post pics.